1. Field of the Invention
The present invention relates to call connection technology. More particularly, the present invention relates to a method and apparatus for attempting to reconnect a call when a call drop occurs in a portable terminal that can support different communication modes.
2. Description of the Related Art
As the popularity of portable terminals continues to increase, manufacturers are developing a variety of functions to satisfy additional user demands. As an example, multi-mode portable terminals have recently appeared on the market. A multi-mode portable terminal is a terminal that can use two or more wireless communication networks.
Conventional portable terminals that support one type of wireless communication network can perform communication within only a corresponding wireless communication network service area. In contrast, the multi-mode portable terminals can perform communication within two or more wireless communication network service areas. For example, dual mode portable terminals can support a Code Division Multiple Access (CDMA) network and a Global System for Mobile communication (GSM) network, so that they can perform communication within both CDMA and GSM network service areas. Accordingly, the dual mode portable terminals can be more widely used than the single mode portable terminals.
However, since the conventional multi-mode portable terminals switch between networks in such a way that they are booted, enter an idle mode, and then perform communication by operation of their menu, they are complicated to operate and require significant time to switch their modes. To resolve these problems, a multi-standby portable terminal has been proposed. The multi-standby portable terminal, unlike the multi-mode portable terminals, can simultaneously support two networks, for example, a CDMA network and a GSM network.
Wireless communication systems, which employ the 2nd generation communication mode, such as a GSM communication mode and a CDMA communication mode, have been used in a wide service area for several years. Accordingly, the basic facilities that support the 2nd generation communication mode have been constructed and are well established.
On the other hand, in order to provide services that a wireless communication system of the 2nd generation communication mode (hereinafter referred to as a ‘2nd generation network’) cannot support, a wireless communication system adopting the 3rd generation communication mode (hereinafter referred to as a ‘3rd generation network’), such as CDMA 2000 communication, Wideband Code Division Multiple Access (WCDMA) communication, etc., is being gradually introduced. In an area equipped with the 3rd generation network, the wireless systems can use the basic facilities for the 2nd generation network and support specialized communication of the 3rd generation network.
However, the 3rd generation network is less widely constructed than the 2nd generation network. In particular, there are still many weak electric field areas and no service areas, with respect to the 3rd generation network. Therefore, when users use a specialized service of the 3rd generation network, for example, a Video Telephony (VT) call service, they frequently experience a call drop when traveling to a weak electric field area or to an area with no service.
That is, while a service, such as a VT call service, is performed through the 3rd generation network, a call drop frequently occurs due to gap areas. In addition, when a portable terminal using a VT call service is moved from the coverage of the 3rd generation network to a service area where only the 2nd generation network is available, its VT call is disconnected.
When call connection is dropped and therefore terminated during the VT call service, a user attempts to manually reconnect the call. That is, when connection of the VT call is enforcedly terminated, the user attempts to connect the disconnected VT call again, without knowing the cause of disconnection. However, when the user moves out of the 3rd generation network service area, the call connection fails and thus the user must attempt to reconnect a voice call using the 2nd generation network.